Evolutionary adaptation to Zn toxicity in populations of Suilloid fungi

Abstract

Summary• Zn tolerance was investigated in populations of four ectomycorrhizal fungi: Suillus luteus , Suillus bovinus , Rhizopogon luteolus and Paxillus involutus. The fungi were collected in pioneer pine forests at 14 different locations, situated along a Zn pollution gradient. Genetic adaptation to Zn toxicity was previously presumed in a population of S. luteus .• Mycelial biomass production was assessed for 235 isolates exposed to increasing Zn 2+ stress. EC 50 concentrations were determined.• Adaptive Zn tolerance was found in the three species from the Suilloid clade and not in P. involutus . The Suilloid fungi collected within 5 km from a Zn smelter were highly Zn-tolerant, in contrast to isolates collected at least 15 km away from a pollution source. Mixed populations with tolerant and sensitive S. luteus isolates were found in a transition zone, between 5 and 15 km from the Zn smelters.• The severe Zn pollution in the surroundings of the Zn smelters has clearly triggered the evolution of an increased Zn tolerance in the pioneer Suilloid fungi. With increasing distances from the Zn smelters, the frequency of Zn-tolerant genotypes decreases.

Arbuscular mycorrhiza of Deschampsia cespitosa (Poaceae) at different soil depths in highly metal-contaminated site in southern Poland

“…However, taking into account very low concentrations of bioavailable forms of Pb (max. 7 mg kg A toxic effect of Cd, Zn and Pb on mycorrhizal fungi as well as their resistance to these metals was also reported by other authors [26,[52][53][54][55]. In the present field experiment with spontaneous vegetation mycorrhizal colonization was high in soil layers with the concentration of bioavailable Cd lower than 20 mg kg −1 (Fig.…”

Copper-Adapted Suillus luteus , a Symbiotic Solution for Pines Colonizing Cu Mine Spoils

“…Although soil fungi (at least saprotrophs) seem to be more resistant to heavy metal contamination than soil bacteria (21), extreme conditions impose selection pressure that may trigger additional evolutionary adaptation in the fungal populations toward even greater resistance. Such genetic adaptation to toxic Zn concentrations has been described previously for ECM fungal populations of suilloid fungi thriving in pioneer pine forests that colonize sites severely contaminated by Zn smelters in northeast Belgium (7). In a dose-response experiment with pines as a host (1), we previously showed that a Zn-sensitive Suillus bovinus isolate developed poorly and failed to acquire sufficient nutrients when the mycorrhizal root system was exposed to Zn concentrations representative of the soluble Zn fraction present in the pore water of soils close to the Zn smelters.…”

Transcriptome analysis by cDNA-AFLP of Suillus luteus Cd-tolerant and Cd-sensitive isolates

“…S. luteus populations from contaminated soils displayed a higher level of tolerance to those metals that were enriched in the soil of origin when compared with populations from non-contaminated soils Colpaert et al 2004;Muller et al 2004). Tolerance mechanisms to heavy metals in ectomycorrhizal fungi seem to include reduced uptake of metals into the cytosol by extracellular chelation through extruded ligands and binding onto cell-wall components, enhanced intracellular chelation of metals in the cytosol, increased efflux from the cytosol out of the cell or into sequestering compartments and enhanced free-radical scavenging capacities (Blaudez et al 2000;Courbot et al 2004;Jacob et al 2004;Bellion et al 2006Bellion et al , 2007.…”

“…Isolates were cultured on solid modified Fries medium as described by Colpaert et al (2004). Uniform inocula (0.5 cm 2 plugs of fungal mycelium) were prepared by 2 or 3 days preincubation of various plugs of mycelium on cellophane-covered agar plates.…”